Pressure sensors for measuring the pressure of a gas or liquid are widely used in many different applications. Capacitive sensors use a diaphragm and pressure cavity to create a variable capacitor to detect strain due to applied pressure, capacitance decreasing as pressure deforms the diaphragm. Common technologies use metal, ceramic, and silicon diaphragms.
Various approaches have been used to expand the measuring range of capacitive pressure sensors. For example, pressure sensors of various sensitivities have been arranged one behind the other with strain gauges. An alternative approach utilizes a capacity manometer with a diaphragm which is freely movable at low pressure and which engages a elastically deformable electrode at or near atmospheric pressure.
Dual range manometers are known which have two signal outputs which are derived from the same sensor input, but in which one output uses different amplification than the other. Other approaches have used two electrodes and two diaphragms.
Known capacitive pressure sensors have limited dynamic operating range of at most four to five decades of pressure due to physical limitations associated with the displacement of diaphragms. In many applications, in particularly in the semiconductor industry, a dynamic measurement range of six to seven decades of pressure is required, e.g. to measure from atmospheric pressure of 103 hPa to a vacuum pressure of 10−4 hPa. This requires the installation of two separate pressure transducers with different measurement ranges.